A hybrid electric vehicle (HEV) is a vehicle that uses an internal combustion engine and a motor, which is driven by a battery, as a power source. The hybrid electric vehicle has attracted considerable attention as a next-generation transport means developed in consideration of exhaustion of fossil fuels.
The hybrid electric vehicle runs at a high speed using the internal combustion engine and runs at a low speed using the motor, which is driven by the battery.
An electric vehicle, which is configured to run only using a battery and an electric motor without using an internal combustion engine, has also attracted considerable attention. The electric vehicle runs by driving the electric motor using electricity stored in the battery. The electric vehicle has advantages in that the structure of the electric vehicle is simple, the durability of the electric vehicle is high, the driving and maintenance of the electric vehicle are easy, and the electric vehicle does not discharge any pollutants, thereby contributing to the protection of environment. For these reasons, the electric vehicle has been widely developed.
The hybrid electric vehicle and the electric vehicle are expected to be increasingly used in that the hybrid electric vehicle and the electric vehicle incur lower operation expenses and maintenance expenses than conventional vehicles using fossil fuels.
However, the battery used in the hybrid electric vehicle or the electric vehicle provides a shorter driving distance than the internal combustion engine due to limitations of its electric capacity. For this reason, it is necessary to provide a battery charging system such that the battery can be continuously charged.
To this end, the hybrid electric vehicle and the electric vehicle use a system for charging the battery through an energy recuperation system based on marginal driving force or braking during high-speed driving. However, the increase in driving distance that can be realized using only such an energy recuperation system is limited.
Consequently, there is a high necessity for technology that is capable of continuously charging a battery of a hybrid electric vehicle or an electric vehicle, thereby increasing the driving distance of the vehicle.